Replacing the manual control unit by the automatic control one is a very stupid idea that will certainly lead to no air conditioning at all because the calculation unit will probably find out there is mismatch of components.
On auto air conditioning, you need additional sensors, probably a different calculator and even certainly a different air conditioning unit. Before you are able to retrofit any of these additional parts you will probably need to remove the full instrument panel. If you want to do by yourself I wish you good luck. Either you remove it fully and you need something to lift it or you remove component by component and there are quite a lot. Someone used to it will need at least half a day with the proper equipment and if you ask a dealer to do it will probably cost you a lot in terms of man hours... And I am not talking about all the risks of rattles of the instrument panel once you have done it.
My advice: if you want auto air conditioning just tick the box when ordering the car and do not try retrofitting afterwards...
And0rea, are you still convinced it could work?

I think there's only 2 sensors, cabin and sun. You would need a wiring loom from a donor car that you can hack to bits and adapt to yours. If you get hold of both schematics it wouldn't take too long to figure it out. Perhaps "real OEM" site may have some clues as to what's involved. I like modding but I would pass on this one.

Hi,
I am convinced that the retrofit could work cause also in the basis AC all the setting (buttons, dials) are electric control and I also learn that the sensors (for example the temperature sensors) are included in the control unit.
I described in detail my opinion in the other thread:http://f20.1addicts.com/forums/showthread.php?t=679018

I agree with XavVD that the simplest solution is to order the car with this option... but I was not aware of the missing auto functionality.

I am also wondering how BWM consider the retrofit on a new car: do they approve this, what about the warranty?

Hi,
my purpose is to retrofit the basic automatic control, I am not interested to retrofit the dual automatic control (in this case the differencies are more...).

Having a look to photos and diagram it seems that the 2 controls (basic not automatic and basic automatic) are very similar; furthermore cause I noticed that also on the basic not automatic control all the regulation are actuated with electric controls, I GUESS (not sure) that the only needed improvement is related to an automatic regulation of the fan speed and this could be easy to be obtained...

Having a look to the automatic basic control (or the the ebay auction...) could clarify.